Vascular Plant Diversity as a Surrogate for Bryophyte and Lichen Diversity

An important issue in conservation biology is the extent to which one group of organisms can function as a surrogate for less well-known groups. We explored the extent to which vascular plant species diversity (both α-diversity, or species richness, and β-diversity, or turnover) and the subgroups of understory, overstory, and ferns can act as surrogates for bryophyte and lichen species diversity. We surveyed 35 sites in a range of forest types in the coastal lowlands of eastern Australia. Fern species richness was strongly positively correlated with bryophyte species richness but negatively correlated with lichen species richness. Fern, bryophyte, and lichen species richness all varied significantly with time since fire, vascular plant cover, and topographic position gradients. Of the other vascular plant groups, the only significant correlation was between overstory and bryophyte species richness. We quantified species turnover using modifications of Whittaker's original measure as well as multivariate techniques. The rate of lichen species turnover was the lowest of all six groups investigated. The other five groups had similar rates of species turnover, although the results were different depending on the emphasis of the measure used. There were significant correlations between the patterns of species turnover of bryophytes and lichens and those of all four vascular plant groups, but none of the correlations was particularly strong. The understory and all vascular plants were the best predictors of the species turnover pattern of bryophytes and lichens, and correlations appeared strongest in wet sclerophyll sites. With respect to management practices, time since the last fire appears to be an important determinant of bryophyte, lichen, and vascular plant diversity, and logging appears to differentially affect the diversity of the different plant categories. A mosaic of logging and fire intervals and intensities appears to be important for maintaining regional diversity.